The Port Authority Policemen's Benevolent Association dispatched its mobile canteen, stress counselor and a contingent of members on their own time to support Boston police at the scene of Monday's bombing attack. Port Authority PBA

BOSTON — After 37 Port Authority Police officers were among more than 2,700 people killed in the 2001 World Trade Center attack, an outpouring of emotional and logistical support from other departments around the country flooded into Ground Zero.

Last night, as part of an ongoing payback since then, the Port Authority Police Benevolent Association sent a group of its members, along with a mobile canteen and the union's stress counselor, to support the Boston officers at the scene of Monday’s bombings.

“Not only do we offer physical comfort when we get up there with our canteen, but emotional support too, because they’re dealing with a huge crime scene, they’re picking up body parts,” said Bobby Egbert, a PAPBA spokesman and retired Port Authority officer. “It starts to manifest itself, some with anxiety, some with restless sleep, an underlying apprehension. And when they start questioning themselves, they’ve got someone to tell them, ‘Hey, that’s normal.’”

The canteen, a pull-trailer with Port Authority PBA markings, is up and running at Boyleston and Berkely Streets, about three blocks east of the two blasts, which were near the Boston Marathon’s Boyleston Street finish line. Officers working the crime scene can help themselves to food, soft drinks, coffee or a seat.

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Basically, Egbert said, “a place to sit, a place to relax, to talk with other cops.”

It’s staffed by a contingent of about 10 Port Authority officers, who made the trip on their own time, Egbert said. They were accompanied by Peter Killeen, a former Port Authority officer who is now a psychological counselor in private practice and retained by the union.

The canteen is pulled by a retired emergency services vehicle dubbed Truck 37, after the officers killed on 9/11, that had been donated to the PAPBA by the Port Authority, which lost a total of 84 police and civilian employees on 9/11.